Down hole safety cutoff valves necessitate provision for re-opening the valve after a shutdown operation utilizing suitable means for equalizing the pressure across the closed cutoff valve. Recently, valves have been developed employing magnetic means for opening the cutoff valve, as for example, the safety cutoff valves disclosed in our U.S. Pat. No. Re. 30,110 granted Oct. 9, 1979 and U.S. Pat. No. 4,161,215 granted to Henry A. Bourne Jr. et al on July 17, 1979. The magnetic cutoff valve shown in our patent relies upon surface equipment to build up pressure above the valve to a value nearly equal to that below the valve whereupon the solenoid can be employed to re-open the valve and maintain it open. Additional surface equipment and time is involved. Bourne et al avoids the need for such surface equipment by utilizing a magnetically operated pressure equalizing facility within their safety cutoff valve. However, certain of these components are located directly in the flow path thereby precluding wire line operations below the valve, impeding the flow, and subjecting important components to fouling and other hazards.
Other proposals have been made for opening magnetically controlled shut off valves in pressurized flow lines of which the following are typical; Boyle U.S. Pat. No. 1,807,191; Hart U.S. Pat. No. 2,693,929; Kramer U.S. Pat. No. 2,969,088; Bullard U.S. Pat. No. 3,100,103; Van Domelen U.S. Pat. No. 3,125,321; Okane U.S. Pat. No. 3,381,932; Keller U.S. Pat. No. 3,405,906; and Sangl U.S. Pat. No. 3,762,683. No one of these constructions with the possible exception of Hart could be installed in a well because the solenoid coil and the armature actuated thereby lie generally normal to the flow path thereby precluding their use in well casings and tubing strings which are subject to severe and rigid cross sectional limitations. Hart is manifestly unsuitable for fluid well applications.